Spiral reverse osmosis device



O United States Patent [1113,542,203

[72] Inventors Robert 1). Hancock; 3,400,825 9/1968 Shippey 210/321Donald T, Bray, Escondido, California 2,870,914 1/1959 Bloch 210/453 :1Appl. No. 663,998 FOREIGN'PATENTS 533 ga e-313% 972,166 10/1964 GreatBritain 55/16 9 [73] Assignee Desalination Systems, Inc. OTHERREFERENCES a or oration of C lif i b m Osbum et al., "New Diffusion CellDesign" from 1 & EC, assignment Vol.46, No. 4, April, 1954, pp 739- 742relied on.

[54] SPIRAL REVERSE OSMOSIS DEVICE Willits et al., Concentration byREVERSE osmosis of Maple Sap" from FOOD TECHNOLOGY, Jan., 1967, Vol. 21,No. I, pp. 24- 26 relied on.

Primary Examiner-Reuben Friedman Assistant Examiner-Frank A. Spear, Jr.Attorney-Thomas D. Lane ABSTRACT: Water purification device having areverse osmosis spiral membrane module with a projecting product wateroutlet tube. The module is disposed within a container comprising atubular casing having an openable end formed by a plug detachablysecured thereto in pressure-tight relationship, the container beingprovided with a feed water inlet and outlet and having an aperturethrough which the module out? let tubeprojects. An annular gasket isseated within the aperture to effect a seal with the outlet tube so thatupon separation of the casing and plug the module can be easily removed.

Pate nted Nov. 24, 1970 Sheet 1 012 M l n 2.4

Imam/7'06;

06597 afl fi m/wag, 30/1 /910 7 HAW v h y Ms 4770 ?57/3 Patented Nov.24, 1970 f 3,542,203

Sheet 2 '01":

fA/l A/IZEJ BY ///5 firraewsys 1 SPIRAL REVERSE OSMOSIS DEVICE tiongradient.

The present invention is directed toward a compact and inexpensive waterpurification device using a reverse osmosis spiral membrane module, thistype of module being now-well known in the art and shown and describedon pages42 and 43 of the 1964 Saline Water Conversion Report of theUnited States Department of Interior, Office of Saline Water, and shownon pages 197 and 198 of theU.S. Government 1965 publication entitledSaline Water Conversion, comprising a record of the Senate hearings onMay 18 and 19, 1965, on Bill $.24 before the Subcommittee On IrrigationAnd Reclamation of the Committee On Interior And Insular Affairs. Thistype of reverse osmosis module is based on a ported tube having spirallywould thereon two selective membranes separated by a granular sheet. Ascreen separator is wound with the membranes to separate the layers ofmembrane formed by the spiral winding. The present inventionisspecifically directed toward a housing for a reverse osmosis spiralmembrane module, with the housing being in the form of a tubularpressure container which is easily separable for removal and replacementofthe module.

Accordingly, it is an object of the present invention to provide animproved water purification device.

It is another object of the present invention to provide a waterpurification device having a reverse osmosis spiral membrane module.

It is a further object of the present invention to provide a device ofthe character described which is compact and inex pensive.

It is also an object of the present invention to provide a device of thecharacter described which is capable of quick disassembly for removal ofthe module.

The novel features which are believed to be characteristic of thepresent invention, together with further objects and advantages thereof.will be better understood from the following description'in which theinvention is illustrated by way of example. It is to be expresslyunderstood, however, that the description is for the purpose ofillustration only and that the true spirit and scope of the invention isdefined by the accompanying claims.

In the drawing;

FIG. 1 is a perspective view ofa device made in accordance with theinvention;

FIG. 2 is a view takenalong line 2-2 of FIG. 1;

FIG. 3 is a view taken along line 3-3 of FIG. 2;

FIG. 4 is a fragmentary view taken along line 4-4 of FIG. 2;

FIG. 5 is a partial perspective view indicating the relationship of themembranesheets in a typical reverse osmosis spiral membrane module;

F IG. 6 is a perspective view of the reverse osmosis module used in thedevice of FIGS. 1 and 2, showing the membrane sheets partially unwound;

FIG. 7 is a longitudinal cross-sectional view of an alternativeembodiment of a device constructed in accordance with the invention-,andI FIG. 8 is a partial sectional view ofa further embodiment of a deviceconstructed in accordance with the invention.

Since the device described herein incorporates a mechanism whichoperates by reverse osmosis, a brief explanation of such osmosis ishelpful and desirable. If a saline solution is separated from pure waterby a semipermeable membrane (one which permits the passage of water butprevents the passage of salt), pure water will flow spontaneously intothesaline solution with the necessary driving force being provided bythe difference in salt concentration between the two solutions. Thisflow will continue until an equilibrium is established. That is, untilthe hydrostatic pressure on the salt solution is just sufficient toprevent the further flow of pure water into the saline water chamber.The movement of pure water into the saline water is called osmosis, andthe pressure at which the flow of pure water ceases is known as theequilibrium osmotic pressure of the saline solution.

The normal process of osmosis can be reversed if sufficient pressure isapplied to the saline solution to overcome the osmotic pressure.Application of a pressure in excess of the osmotic pressure will causepure water to flow out of the saline solution in a direction opposite tothe osmotic flow, hence the term reverse osmosis." The driving potentialin this reverse case is pressure while in normal osmosis, the drivingpotential is the difference in salt concentrations between the twosolutions.

Referring now to the drawing, there is shown in FIG. 1 one preferredembodiment of a device constructed in accordance with the invention. Thehousing is denoted generally by the numeral 10. The housing comprises acentral cylindrical tubular section 11, capped at its ends by an outletcap 12 and an inlet cap 13. The terms inlet" and outlet as applied tocaps 12 and 13 are used for convenience only to distinguish the caps 12and 13. It will be clear from the discussion hereinafter that either endof the device may be utilized for inlet or outlet purposes. The section11 and 12 and 13 may be made of a multitude of materials. However, foreconomy, in the preferred embodiment shown in FIG. 1, plastic such aspolyvinylchloride (more commonly known as PVC) is utilized as thehousing material. The inside diameter of section 11 may be of anyconvenient measurement and will have a predetermined size to accommodatethe desired capacity of the device as will be described hereinafter.Also, the length of section 11 may be of any convenient size and will bepredetermined according to capacity desired. Inexperiments with devicesas shown in FIG.

1, the inventor has found that diameters in the range of 2 inches to 6inches and lengths in the range of 12 inches to inches are quitepracticable for an efficient and compact unit. The inside diameters ofcaps 12 and 13 are substantially equal to but greater than the outsidediameter of section 11. Thus, for installation the caps 12 and 13 arepress fitted onto section 11, as shown best in FIG. 2, and cemented inplace by applying glue to the surface contact parts prior to assemblage.Openings 17 and 18 are radially threaded through section 11 and the caps12 and 13. The openings 17 and 18 are adapted to receive an outlet pipefitting 21 and an inlet pipe fitting 22 which provide the inlet andoutlet means for the unpurified water as will be described hereinafter.The pipe fittings 21 and 22 are threaded into openings 17 and 18 andsecured in place. Alternatively, the pipe fittings can be inserted intounthreaded openings properly sized and cemented into place withoutadverseconsequences. Also, fittings other than pipe fittings may beutilized, depending on the desired installation.

' Outlet cap 12 has provided therein a central opening 24 to accommodatethe product water line tube 25 of the osmosis module 26. The opening 24is substantially equal to but greater than the diameter of the tube 25so that tube 25 can be press titted through opening 24 to create analmost sealed condition. To provide a positive seal, as can be best seenin FIG. 2, groove 28 is formed in opening 24 and an Oring 29 inserted ingroove 28. The O-ring 29 is compressed against tube 25 and forms a sealtherewith. Theshape of the cap 12 is not critical, and the generallyrounded shape shown was chosen for its availability and its safety inhandling because of the absence of sharp edges.

The inlet cap 13 is adapted to receive a plug 30 detachably securedthereto and which forms an openable end of the pressure container orhousing 10. The cap 13 is a section of cylindrical tubing which extendsbeyond the end of section 11 of the housing 10. One conventional type oftubing is the standard slip fit coupling for the size of pipe used forsection 11. Another convenient approach is to utilize a standardreducing tee where the reducing tee takes the place of opening 18. Asmaller diameter section 31 can be formed in cap 13 to provide acircumferential shoulder 32 to limit the depth of insertion of section11 into cap 13 during the press fit assembly.

The osmosis module 26 is retained between the cap 12 and the plug 30.Plug 30 hasa diameter substantially equal to but less than the-insidediameter of cap 13 so that the plug 30 may be easily fitted into cap 13.Two circumferential grooves 37 and 38 are defined in plug 30. O-rings 39and 40 are contained in grooves 37 and 38 to provide a good seal betweenplug 30 and the inside surface of cap 13. A handle 42 is provided onplug 30 for ease of installation and removal of the plug 30 from cap 13.As an alternative to handle 42 a hole can be drilled part way throughplug 30 at its center, this hole being threaded with a convenientmachine thread. For removal of the plug 30, a standard threaded eyeboltis screwed into the hole and used as a handle.

A circumferential groove 43 is defined in the inner surface of cap 13.The groove 43 is adapted to receive a snap ring 45. The groove 43 mustbe located so that the plug 30 can be inserted between the groove 43 andthe end of the module 26. The snap ring 45 is of a conventional type,and when installed in groove 43 retains the plug 30 in cap 13 whenpressure is applied to the water inside the housing 10. Snap ring 45 hasenlarged ends 45a which are adapted for tool insertion to engage andremove ring 45 from its groove 43. Thus, it is a simple matter to removethe ring 45 and the plug 30 to allow replacement of the reverse osmosismodule 26. For units which are intended for more or less continuous use,this replacement feature provides for substantial economic savingscompared to a unit which is permanently sealed.

Turning now to the reverse osmosis module 26, as can best be seen inFIGS. 2, and 6. Module 26 has as its supporting structure a centralproduct water tube 50. The term product water is used for convenience,since, as will be described hereinafter, the purified water will passthrough this tube 50 to the outlet tube 25. The 'tube 50 may be made ofany rigid corrosion-resistant material. In the preferred embodiment, thetube 50 is made of plastic such as PVC. Tube 50 is sealed at one end bya cap 51. The cap 51 is also made of plastic and is press-fitted overthe end of tube 50 and cemented to form a good seal. A special outletcap 53 is similarly press-fitted and cemented at the other end of tube50. The cap 53 has an integrally formed tube section 25 which, asdescribed hereinabove, projects through cap 12. The tube 25 is the waterproduct outlet, that is, the purified water exits through tube 25. Aseries of ports or apertures 55, as can be readily seen in FIG. 5, aredrilled or otherwise formed along the central section of tube 50.Attached longitudinally to tube 50 is a sheet 60 defining two sections60a and 60b which are semipermeable or reverse osmosis membranes. Thetwo sheet sections are formed by taking a single long sheet and wrappingit around the tube 50 and extending the ends out to form two sheetsections 60a and 60b. The sheet sections are arranged so that theproduct water side surfaces of membrane sheet 60 face each other.Extending between the reverse osmosis sheet sections 600 and 60b is asheet 65 of granular material. In the preferred embodiment, the granularsheet 65 comprises a base of sheet material with glass beads affixedthereto. An adhesive is placed on the granular sheet 65 all around theedges and around the central tube. The adhesive penetrates and fills thepores of granular sheet 65 and contacts the product water side ofmembrane sheet 60, effecting a seal between membrane sheet 60 and thegranular sheet 65, and between both to the central tube 50. Thus, as canbe readily seen, ports 55 communicate only with product water. That is,because of the foldover construction of the membranes, as discussedhereinabove, the unpurified water is separated from the granular sheet65 by the membrane sheet 60. Accordingly, only water that has passedthrough membrane 60, i.e., product water, can reached ports 55.

Also attached longitudinally to the tube 50 is a plastic screen 67 whichis an outside layer when the combined sheets are spirally wound aroundthe tube 50, the screen 67 serving to space apart the layer of windings.The sheets 66, 65 and 67 are spirally wound around the tube 50 to form acompact module. The length of the sheets and the diameter of the moduleare determined by the desired capacity of the module.

In the completed module, several cylindrical layers are formed as aresult of the spiral winding. Each cylindrical layer provides a doublemembrane facing the granular sheet 65. The plastic screen 67. keeps theindividual cylindrical layers separated. The completed winding is keptintact by wrapping the outer part of the roll. In the preferredembodiment, a strip of plastic adhesive tape 70 is utilized. A moredetailed ex planation of the construction and operation of such reverseosmosis modules can be found in the 1965 Saline Water Conversion Reportof the U.S. Department of Interior, Office of Saline Water.

Installed within fitting 21 in the illustrated embodiment is an orificeto reduce the pressure of the unpurified water to atmospheric pressure.The orifice is of conventional design and is sized to provide thedesired flow of outlet water. The pressure drop within the housing 10before the orifice is small, preferably in the range of 0.5 to L0 p.s.i.The lower the pressure drop before the orifice, the more efficient theunit since more pressure is available to drive the unpurified waterthrough the membrane 60. In practice, however, a loss of 0.5 to 1.0p.s.i. is not critical since system operating pressures are generallyabove 30 p.s.i.

In operationof the unit, the unpurified water, which may be sea water orother brackish water, enters at fitting 22 and exits at fitting 21. Thepressure of the unpurified water remains at practically its inputpressure because of the orifice 75. The unpurified water flows throughthe module and because of plastic screen 67 it is present at each layerof the spiral. Because of the input pressure of the unpurified water,the water is diffused through the layers of the membrane sheet 60 andbecomes purified or product water. The productwater flows through thegranular layer 65, spirally inward to tube 510 through the ports 55 intothe inner part of tube 50, and exits through outlet tube 25.

Looking now to FIG. 7, an alternative embodiment of the invention isshown. The advantage of the embodiment of FIG. 7 is that all waterlinesare at one end of the device to permit installation in relativelyinaccessible locations. In this embodiment the housing comprises a maintube section and a cap 81. The tube section 80 is made of someconvenient inexpensive material, such as glass or plastic, PVC forexample, and is shaped similarly to a chemical test tube, i.e., with ahemispherical end 82.

The open end 83 of tube 80 has threads 84 formed thereon. Cap 81 isinternally threaded to engage with threads 84 of tube 80.'The cap 81 hasreduced diameter internal sections to form mounting surfaces for thetube 80 and a reverse osmosis module 87. The module 87 is similar to themodule hereinabove described. Module 87 is retained in place by sleeve88 which is supported by a reduced diameter section 89 of the cap 81.Openings 92, 93 and 94 are provided through the cap 81 for theunpurified water inlet 1.00, the product water outlet 101, and theunpurified water outlet 102, respec tively.

The tube 101 is positively sealed to the product water output of module87 by means ofa cap 110 which is pressed fit to the module 87, andwhi'chcontains therein O-ring 111 as a seal. An alternative arrangement is theuse ofthe same module and fitting 53-25 shown in the FIG. 2 embodimentand an O- ring seal in the cap 81 similar to the groove 28 and O-ring 29seal of the FIG. 2 embodiment. For convenience in packaging, opening 92has a slanted portion 103 to form a path of communication between theunpurified water inlet and the volume between module 87 and tube 80.Inside tube 80, proximate the end portion 82 thereof, the illustratedembodiment is provided with packing 105 which is fiber or felt or thelike to serve as a filter for the incoming water. An orifice 107 is provided in the unpurified water outlet 102, to reduce the pressure ashereinabove described. The cap 81 is sealed to the end of the tube 80 bymeans of an O-ring 85.

Thus, in operation of the device of FIG. 7, unpurified water entersthrough inlet 100 and passes between tube 80 and module 87, throughpacking 105 and into the module 87. Some of the unpurified waterdiffuses through the membrane layers of the module 87, in the mannerdiscussed hereinabove and exits as fresh product water at the outlet Theremaining unpurified water exhausts through the outlet 102 after havingits pressure reduced by the orifice 107. The packing 105 filters largeparticles from the product water and helps to prevent clogging of theunpurified water passages in the module 87. An alternative arrangementis to locate the cap 81 entirely within the tube 80, or an extensionthereof, similar to a plug and to utilize a snap ring arrangement asdescribed above to hold the plug in place.

As an alternative to the device shown in FIG. 7, the tube section 80,instead of being provided with external threads, can have a flared endprovided with internal threads. Such an embodiment is indicated in FIG.8 of the drawing which shows only the flared open end 121 of a tube 120,the cutaway portion of the device being identical with that shown inFIG. 7. The enlarged end 121 is internally threaded at 122 for receptiveengagement of an externally threaded cap 125. The cap 125 is providedwith a series of longitudinal passageways or openings 126, l27and 128,corresponding respectively to the openings 92, 93 and 94 in the cap 8].Into these openings are inserted the various inlet and outlet tubes100-102 in the identical manner shown in the device of FIG. 7. Theopening 126 has a slanted portion 129 to form a path of communicationbetween the unpurifled water inlet 100 and the volume between module 87and the tube 120. As in the embodiment of FIG. 7, the module 87 isretained in place by a sleeve 88 which is supported by a reduceddiameter section of the closure cap.

The threaded portion of the end 121 of tube 120 defines a shoulder 130for seeking of O-ring 85 to effect a seal between the closure cap 125and the tube 120. Operation of the device of FIG. 8 is identical withthat of the device of FIG. 7, the primary difference being only in theconstruction wherein the closure cap is threaded into the tube ratherthan onto the tube.

We claim:

1. Water purification apparatus comprising in combination:

a. a reverse osmosis spiral membrane module including a membrane sheetassemblage wound onto a sealed tubular casing and covering apertures inthe longitudinal surface thereof for the flow of product water throughsaid membrane and said apertures into said casing, said casing having anaxially projected outlet tube at one of its ends for the removal ofproduct water therefrom;

b. a tubular pressure container having an end defining a centralcircular opening therethrough with a circumferential groove intermediatethe inner and outer surfaces of the casing end, and an annular gasket offlexible resilient material disposed in said circumferential groove andextending into said circular opening around its periphery, said modulebeing disposed within said pressure container with said outlet tubeextending through said circular opening and projecting from saidcontainer with said annular gasket forming a pressure-tight seal to saidoutlet tube, said container further including feed water inlet meansnear one of its ends and feed water outlet means near its opposite end;and

. said tubular pressure container having an openable end formed by plugmeans detachably secured thereto in pressure-tight relationship wherebysaid module can be removed from said container upon detachment of saidplug means said plug means being spaced apart from the adjacent end ofsaid module to permit passage of water to be purified longitudinallythrough said module.

2. Water purification apparatus as defined in claim 1,

wherein said plug means defines a cylindrical body inserted into thetubular openable end of said pressure container, the

diameter of said cylindrical body being slightly less than the innerdiameter of the open end of said tubular container, said cylindricalbody having spaced apart circumferential grooves each having seatedtherein an annular gasket of flexible resilient material, these gasketsprojecting circumferentially from said cylindrical body into contactwith the inner wall surface of said pressure container to form apressure-tight seal.

3. Water purification apparatus as defined in claim 2, wherein theopenable end of said pressure container further defines an innercircumferential groove into which is fitted removable expansion ringmeans to retain said cylindrical body within said openable end of saidpressure container.

